1. Field of the Invention
The present invention relates to a vane pump used for a power steering apparatus or the like of a motor vehicle.
2. Description of the Related Art
As a vane pump for assisting steering force in a power steering apparatus of a motor vehicle, there is a structure having a rotor which is fixed to a pump shaft inserted to a pump casing so as to be rotated, and moves a multiplicity of vanes in a radial direction within a pump chamber to pressurize a working fluid sucked into the pump chamber so as to discharge, and having a flow control valve which returns a surplus working fluid in a discharge side high pressure passage communicated with the pump chamber to a suction side low pressure passage communicated with the pump chamber. In this vane pump, it is possible to control discharge amount of the working fluid discharged to a power cylinder side of the power steering apparatus to a fixed amount due to an existence of the flow control valve.
In the conventional art, in a crossing portion between a return passage of the flow control valve and a suction side low pressure passage provided in the pump casing, the bottom surface of the low pressure passage is set to be shallow and above a bottom surface of the return passage. Then, in this setting, particularly at a time of high pressure relief, a vibrating phenomenon is generated in which the flow control valve is hit by an inner surface of a receiving hole within the receiving hole provided in the pump casing, whereby an abrasion of the flow control valve is promoted and a service life is reduced.
An object of the present invention is to prevent a vibrating phenomenon in which a flow control valve is hit by an inner surface of a receiving hole provided in a pump casing within the receiving hole, in a vane pump.
In accordance with the present invention, there is provided a vane pump comprising:
a rotor fixed to a pump shaft inserted to a pump casing so as to be rotated, moving a multiplicity of vanes in a radial direction within a pump chamber, and pressurizing a working fluid sucked into the pump chamber so as to discharge; and
a flow amount control valve returning a surplus working fluid in a discharge side high pressure passage communicated with the pump chamber to a suction side low pressure communicated with the pump chamber,
wherein in a crossing portion between a return passage of the flow amount control valve and a suction side low pressure passage, a bottom surface of the low pressure passage is set to be below a bottom surface of the return passage.